Ice Mountain: “Little Blow Holes” — Chapter 1
Everything below belt-line felt cold as I climbed up the lower flank of the Gorge’s Shellrock Mountain on the morning of May 28, 2017, on a day that would eventually become hot and still. I was completing the second day of a survey for American pikas, the rabbit-related, talus-dwelling mammals so characteristic of high-elevation and cool-temperature zones of the American west. Oddly, the species exists in the Columbia River Gorge at lower elevations (almost sea level) than anywhere else in the US. Why has remained a mystery.
As I continued scanning the talus slope and forest margins, I saw that all the leaves within three feet of the ground were being agitated by the steady flow of cold air flowing downhill, like a sheet-flow of water over the land surface. The air above that three foot level was contrastingly motionless and relatively warm. Upon bending down into the cold layer and examining the talus surface, I felt the cold air emerging from the talus itself, springing like invisible water from the countless openings.
What was causing the generation and emission of this near freezing air, and could it somehow be related to the seeming out-of-place existence of cool-loving pikas at near sea level in the Gorge? My interest grew as I walked back down the old road from the survey site.
The Cool-Loving Pika
Most everyone who has hiked, climbed or driven through the high mountainous regions of the western US has treaded upon American pika territory. In the northern coastal regions of British Columbia, the populations range from near sea level to over 13,000 feet in those high and cold latitudes. Farther south, in the lower latitudes of Nevada and California, the lower limit of their range begins at about 6,000 feet. In our portion of the central Cascade Mountains of Washington and Oregon, pikas commonly occur at elevations of 4,000 feet to above timberline. Here in the Gorge, however, many people have been surprised to hear their familiar call along the Columbia River near sea level, at places like Shellrock Mountain, Herman Creek, and even the heavily used trails around Multnomah Falls.
There are many fascinating aspects of pika biology, but the chief consideration of this article is their narrow range of temperature tolerance. Pikas, like other members of the rabbit family (i.e., lagomorphs), are limited in their ability to regulate body heat. Most important, they are unable to cool their body temperature by panting or sweating. If unable to find thermal shelter and shade on a day humans might find comfortable (i.e., 78 degrees F), they can become stressed (hyperthermic) and die in as few as six hours. Nor do they tolerate extreme cold, and researchers have concluded that they are dependent on long-lasting winter snow packs above their winter dens to provide igloo-like insulation from cold air and the rigors of rain and freezing rain. This has led researchers to conclude that extreme temperature (both high and low) is likely the most important ‘limiting factor’ determining what elevations and latitudes pikas can survive. At first glance, it would seem doubtful that pikas could survive in the lower elevations of the Gorge, because summer air temperatures can be very warm, and winters have periods of extreme cold, no snowpack, heavy rain and periods of freezing rain.
Photo credit: Will Thompson/ USGS
Pikas do not hibernate. Instead, they keep their heat-generating metabolism going throughout the winter by staying active and subsisting on a wide variety of plants foraged and stored in “hay piles” during the previous summer. In accord with their unique physiology, they have evolved a partially underground lifestyle, similar to cave dwellers. And in actuality, the talus rock pockets they inhabit are like caves with respect to having relatively constant and moderate year-round temperatures. Talus is essentially blocky rock debris that has been shed from steep mountain walls, which gradually accumulates in pediments along the lower mountain slopes. Because the rocks are relatively uniform in size, there is considerable open space between the blocks that insulates the interior pockets from sun exposure, wind, moisture, and other outside conditions. While pikas spend a great deal of time outdoors collecting and eating plant forage, they are highly dependent on their buffered, underground pocket environment for year-round protection from predators, rearing their young, keeping dry, and especially escaping the extremes of summer heat and winter cold.
But if explaining pika presence in the lower elevations of the Gorge was solely based on their biological adaption to use of talus shelter, why is the population mostly restricted to the 20 mile-long, Oregon-side segment between Multnomah Falls and Shellrock Mountain? In fact, seemingly suitable talus geologies occur throughout the Gorge, both east and west. The answer to the pika riddle must be approached broader, and in the context of a complex biogeography question.
Biogeography is one of the more interesting realms of biological science, as it merges the fields of ecology, climate, geology, evolutionary biology, and physical geography to explain why species occur in specific patchworks on the landscape. It is a field that originated with the early exploration of our planet, when great European expedition-based biologists like Alfred Russel Wallace began noting and trying to explain why plant and animal communities changed with latitude, elevation, aspect, and other characteristics of the geographies they traversed.
The more I thought about what I had seen at Shellrock Mountain on that soon to be hot Gorge day, the more I suspected that the mountain’s breath of cold air might hold the answer to solving the pika riddle. Before long, I was driving back east along the 10 mile stretch of interstate I-84 leading to Hood River and White Salmon, with questions for Google and knowledgeable scientists. What I subsequently learned, and the theories hatched to explain the Shellrock situation, will be outlined in the following chapters dealing with heat transfer in talus slopes, permafrost, Gorge history, and Gorge meteorology.
Ice Mountain: The Chimney Effect — Chapter 2
Some hillsides, like all caves, inhale and exhale air due to how differences in outside temperature and barometric pressure act upon their interiors. Air pressure and temperature changes that occur in mountain features like talus slopes have been most actively studied by scientists in mountainous regions of the world (particularly in the Alps of Europe), where landscapes are dominated by high peaks and valleys, and the understanding of glaciers, permafrost, rock falls, talus slopes, and water supplies is critical to living in such places.
Upon noticing the unusual venting of cold air from the lower slopes of Shellrock Mountain, I returned home, and began reading the findings of the various scientists involved in the study of talus slope dynamics. I learned that there is indeed a well-documented physical process observed in “cold talus slopes” that causes them to draw cold air into the toe of the slope in winter, and emit cold air from the toe in summer.
This reversible air circulation process, known as the “chimney effect”, was first scientifically described by Alpine explorer Horace-Bénédict de Saussure in the 16th century, after observation of out-of-place ecologies, including cold-stunted trees, dwarf forests, mosses, and typically higher elevation plant species, at the bottom of some mountain slopes. And too, people even before Saussure’s time would have recognized and found economic uses for cold talus, including the storage of perishable foods and ice during the summer.
Swiss researchers Sébastien Morard, Reynald Delaloye, and Christophe Lambiel describe the cold talus chimney effect in their 2010 paper from Geographica Helvetica, entitled “Pluriannual thermal behaviour of low elevation cold talus slopes in western Switzerland”, a portion of which is quoted below.
“Variations of both direction and velocity of the airflow in accumulations of loose sediments are primarily controlled by the thermal contrast between the outside and inside (ground) air causing a gradient of driving pressure. The airflow direction reverses seasonally. During winter, an ascent of relatively warm light air tends to occur in the upper part of the debris accumulation. This leads to a dynamic low (a depression) in the lower part, causing a forced aspiration of cold external air deep inside the ground even through a thick – but porous – snowpack. A gravity discharge of relatively cold dense air occurs during summer in the lowermost part of the debris accumulation, preventing the ground surface temperature from rising significantly above 0°C in this section of the loose sediment accumulation. As a consequence, a diffuse aspiration of external warm air occurs in the upper part of the slope”.
A diagram from their paper that illustrates the process follows. The abbreviation Tao indicates outside air temperature and Tai indicates temperature inside the talus slope.
These and other researchers have shown that the chimney effect is a process that can be responsible for the formation of perpetually frozen ground (permafrost) and ice in the base of some cold talus slopes. This sub-zero temperature anomaly is accompanied by a corresponding warm zone in upper sections of the same slopes. Interestingly, the emission of the upward trending warm air from the slope’s interior can be witnessed in winter by the absence of snow surrounding the warm vents. A well-studied example of cold talus is found at the Creux-du-Van talus slope in the Jura Mountains of Switzerland at an elevation of about 3500 feet, which is significantly below the 8000 foot level of discontinuous (i.e., sporadic) mountain permafrost for this latitude in the Alps (about the same latitude as Mt. Rainier).
On first impression, the formation of ground permafrost and ice seems impossible in places like Creux-du-Van, where mean annual air temperatures are 42 degrees F, and regional mean annual ground temperatures are also well above freezing. Year-round ice seems further unlikely in ground where cooling must first overcome the earth’s natural heat. The recognized explanation for this mysterious cooling is that the chimney effect can cause drastic over-cooling at the base of the slope in winter, enough to surpass summer heating. The effect is enhanced when fall and early winter snow packs are lacking while temperatures are below freezing. This allows cold air to freely enter at the beginning of winter, and become later trapped by the snow cover. The colder the ambient winter air, the bigger the thermal gradient between the inside and outside of the slope, and the faster cold air is drawn up into the slope’s base. Likewise, the warmer the summer, the faster the upper portions of the talus slope are warmed in response to cold air draining from the base. Researchers also comment on the existence of a moss layer covering the bottom of cold Alpine talus slopes, similar to what we witness in the Columbia River Gorge. The observation is of interest, since not only is the moss dependent on the slope’s output of cool air, but it may also be responsible for the cold talus effect since it insulates and seals the surface of the porous talus so that it can act as a defined conduit for air exchange.
About one month after my first notice of apparent cold talus at Shellrock, I again travelled to the site on the hot afternoon of July 5, 2017, armed with a long-probe electronic thermometer, to try to measure the temperature of the cold air draining from the talus veneers on the mountain’s north side. Cold air was found to be venting from many of the mountain’s talus slopes, most in the range of 40 degrees F. As the day was ending, I decided to try to sink the temperature probe into the base of one last slope. Soon, and to great surprise, the thermometer’s screen displayed a snowflake symbol, indicating that the probe had encountered a truly frozen zone only one foot below the rocky surface. This same monitoring site continued to show sub-freezing conditions until the first week of August, at which time the foot-deep temperature began to rise slowly above 32 degrees F.
Here, with discovery of an apparently active chimney effect, it was starting to appear that cold talus was indeed present at Shellrock Mountain, and quite possibly deep permafrost. With this, the riddle posed in the first chapter (i.e., how is it possible that American pika can survive in the low and warm elevations of the Columbia River Gorge?) seemed to be gaining a possible explanation. But with this discovery, a much larger ultimate question arose: how was it possible, in the first place, that strongly cold talus and likely permafrost could be present at this incredibly low altitude (120 feet above sea level) and at this middle latitude? This question will be explored in the fifth chapter, which deals with the theory that our unique Gorge climate and topography may be responsible. Before that, however, the next chapter will explore the possibility that the landform I had come across was a periglacial rock/ice feature. The fourth chapter will explore whether any historical records may support the existence of ice and periglacial activity at Shellrock Mountain.
Ice Mountain: Periglacial Ice on Shellrock Mountain? — Chapter 3
One western scientist’s findings have special relevance to understanding pika presence in the Gorge. Connie Millar of the US Forest Service’s Pacific Southwest Research Station in Albany, California has researched the ecology of American pika in the talus landscapes of the Sierra Nevada and western Great Basin for the past 15 years. Her work has centered on development of rapid assessment protocols for identifying potential pika habitat via on-site analysis of climate, ground temperatures, landscape type and geology. With such understanding, the USFS hopes to improve its ability to decide whether certain land management strategies will have impacts on pikas, possibly under a changing climate.
During examination of hundreds of rocky pika occupations in the Sierra Nevada and Great Basin (at altitudes ranging from 5,593 to 12,752 feet), Millar concluded that most (82%) are in close proximity to rock glaciers or similar rock/ice (i.e., periglacial) features. Also observed was the fact that pikas are typically found near the base of ice-cored talus slopes and rock glaciers, given the presence of both suitable thermal habitat and proximity to the forefields they use to collect forage. Based on this, Millar has confirmed that such rock/ice periglacial habitats are optimal for American pika
I first began suspecting that the cold talus feature found at Shellrock might be ice-cored talus after reading descriptions of these geologic features, and revisiting the site for closer examination. Although much debated, most geologists agree that year-round ice can form in mountainous or arctic terrains as a result of two distinct processes. The first is termed “glacial”, which is the familiar process that starts with snowfall, snow accumulation, and gradual transformation to solid ice as snow depth increases. The second process is known as “periglacial”, which is not dependent on snow accumulation. Instead, periglacial ice is formed when precipitation or melt water enters and freezes within an already frozen underground rock or soil matrix. Common types of periglacial features identified by geologists include rock glaciers, boulder streams, ramparts, patterned ground, and ice-cored talus.
The Shellrock Mountain feature seems to fit the description that geologists have assigned to periglacial ice-cored talus, or potentially a very small rock glacier. It occurs at the base of a massive talus slope, displays a slightly over-steepened front face and sidewalls, is longer than wide, and appears to be frozen. Finally, it shows signs of past movement, which during construction of Interstate 84 during the 1950s-1960s required construction of a steel reinforced earth wall to protect the highway. I hypothesize that periglacial ice forms here when precipitation falls on upper portions of the slope, sinks into the relatively warm upper talus interior, flows downslope along the bedrock interface, and finally intercepts freezing temperatures in the lower core. It is likely that most of the water infiltration and freezing occurs in winter with the on-set of cold temperatures, rain, and snow. Remember that chimney effect cooling is highest during winter, when cold air is actively drawn into the base of the slope while warm air is discharged from the upper slope.
Ice Mountain: “Shellrock Mountain Rests on Ice” — Chapter 4
Upon finding documentation of the formation of periglacial ice at the base of some low-elevation talus slopes in Europe and elsewhere, I became interested in monitoring the Shellrock slope using the methods of European researchers to prove the existence of ice and permafrost. But before that investment of time and money (or trying to convince others to be party to it), it made sense to first determine whether these conditions had ever been reported at Shellrock Mountain or other Gorge locales, perhaps during a colder climatic past. Had earlier pioneers noted this apparently remarkable geological feature?
One well-known Columbia River Gorge historical event immediately came to mind, that being the winter 1884-85 stranding of a passenger train between Shellrock Mountain and Starvation Creek (see 1922 photo below, courtesy of The History Museum of Hood River County). During that unusually harsh winter, an east wind-driven storm resulted in 15-20 foot deep flows of ice pellets that froze into one solid mass of ice, eventually requiring blasting to remove. Passengers were stranded for 3 weeks, until the good citizens of Hood River were able to come to their rescue with picks, shovels, black powder, and food.
Photo Credit: History Museum of Hood River County
While it does not seem likely that this specific type of weather pattern could be responsible for the buildup of periglacial ice, it is indicative of atypical meteorological patterns in the vicinity of Shellrock Mountain that still occur. Travelers along I-84 witnessed smaller deposits of welded ice pellets in this area as recently as spring 2017, and long after evidence of ice and snow had disappeared from other Gorge locales. ODOT maintenance crews at Cascade Locks still consider this stretch of road their worst winter maintenance challenge.
Upon continued research, it was exciting to find a much more relevant reference to potential periglacial ice contained in William H. McNeal’s 1953 book entitled “History of Wasco County”, which relates stories from construction of the early roads through the Gorge. In one chapter, McNeal describes the almost insurmountable barrier posed by Shellrock Mountain to construction of the 1915 Columbia River Highway. Within that passage, McNeal states “Shellrock Mountain rests on ice”. With that exciting tidbit, I began contacting people who might have engineering records going back to construction of the first roads, including the Historical Columbia River Highway.
Of all the people contacted, the most valuable assistance came from Kristin Stallman, who until recently worked as ODOT’s Historic Columbia River Highway Trail project coordinator. I soon found that Kristen maintained a large library of historical information related to construction of the old highway. The first document she provided gave strong support to the statement made in McNeal’s book. This was the transcript of a 1967 interview conducted by historians Ivan Donaldson and Wayne Gurley, with Glenn Kibbe and Marshall Newport, two men who had actually worked on construction of the highway. Kibbe headed the construction company “Kern and Kibbe”, which had the contract to build the section of the Columbia River Highway between the Multnomah line and the City of Hood River. His interview documented many problems encountered during construction, many revolving around the impacts of excessive water on slope stability at places like Ruckel Creek and Herman Creek. Beyond that, Kibbe, Marshall, and the interviewers devoted a lot of discussion to ice and water-related talus instability at Shellrock’s west end. I was especially excited to come across the portion of the interview inserted below, which seems to describe the slope that is the subject of this article:
“Gurley: I was wondering when they were working on the highway down here they took a lot of material off that sliding slope where it had been sliding so bad and right in there. When I came over here a fellow took me back there and there were little openings in the rock and you could feel the cold air rushing out of there just as if it was off of ice. Kinda like little blow holes.
Newport: Ice is supposed to be in there, isn’t it Glen?
Gurley: And that’s where they found it, according to drillings”.
Gurley’s reflections on 1915 are very telling. First, it’s obvious that more than a century ago, he had witnessed the same strong cold talus effects that I observed on May 28, 2017. Second, he provided evidence that engineers and/or contractors working on construction of the Columbia River Highway intercepted ice during either construction or exploratory drilling.
A further exchange from the interview gives still more historical evidence of subsurface ice at Shellrock. This portion is of special interest, given that Kibbe ventures to say the ice was not “glacial”. With that, he was likely saying that the ice was not laying on the surface in a pure state, as might be seen on the glaciers of Mount Adams or Mount Hood. Instead, he seemed to be describing an ice feature that had a large percentage of rock and soil material in its composition. Indeed, his description better fits the appearance of thawing, shallow periglacial ice, perhaps a geological process known as solifluction occurring over the slope’s frozen core.
“Kibbe: I wonder if there’s still ice in that mountain?
Gurley: From what most of the geologists say, I think there is.
Kibbe: When I was here in 1917 up to 1920, while I was here, this this stuff was not like a glacier. It was like what you might call a melting ice and that’s where you got your slides. In the summer she’d get warm and melt, bring down gravel all the time. We built high walls to catch it, but I guess they all filled up and I guess they had to take them out”.
Ice Mountain: A Wind Gap Between Wind Mountain and Shellrock Mountain — Chapter 5
Windsurfers, fishermen, barge pilots and even motorists have experienced the turbulent culmination of Gorge topography and weather occurring west of the narrow gap that constricts the Columbia River between Wind Mountain to the north and Shellrock Mountain to the south. At only one-third of a mile across, this gap is the narrowest found along the Columbia River as it cuts through the Cascade Range between the cities of Cascade Locks and Hood River. The north-south trending Cascade Range crest is such a dominant landscape feature, it actually creates separation between the Pacific Northwest’s two major climatic patterns, the wet maritime regime to the west and the dry continental regime to the east. Very important to the context of this article, the Columbia River constitutes the only near sea level pathway through the Cascade Range, and represents a very active air conduit between these two major climatic regions.
The individuals having perhaps the most knowledge of Columbia River Gorge weather are Justin Sharp, who as a graduate student at the University of Washington, worked with Professor Clifford Mass to publish a detailed 2004 article entitled “Columbia Gorge Gap Winds: Their Climatological Inﬂuence and Synoptic Evolution”. Not surprising, the main aspect of Gorge weather they examined was the east wind pattern of winter. Most of the background information in the next paragraph can be attributed to their work.
Easterly “gap winds” in the western Gorge are partially driven by eastern high-pressure systems pushing dry and cold continental air to the west, and western low pressure systems pulling air into the maritime area west of the Cascades. While these large-scale “synoptic” weather patterns often initiate the westward flow, the wind can be strengthened by the unleashing of large masses of cold and dense air from the Columbia Basin, which flows hydraulically (by gravity) down the Columbia River valley from its contributing basins. As we all know, these miserably persistent east wind patterns are often accompanied by atmospheric inversions, and weeks when the entire Columbia Basin and eastern Gorge is overcast.
An air inversion is simply a weather pattern characterized by a layer of warm (and therefore relatively buoyant) air above a layer of dense cold air at the land’s surface. As this huge but thin layer of cold and dense air moves west, it becomes deeper as it dams-up against the Cascade Range, and surface air pressures become even greater. Consequently, the cold air begins to rush through the narrowest parts of the Columbia Gorge and the lower passes through the Cascades. The air movement results in high velocity gap winds in the western Gorge that commonly exceed 35 mph, but occasionally gust to over 100 mph at places like Crown Point. As the air moves through the gap, it increases velocity while moving from high to low pressure in a very short distance. In a recent correspondence with Sharp, he related that the pressure differentials that develop at the Wind/Shellrock gap may be as high as one millibar over a distance of three kilometers, which is higher than most meteorologists think even possible.
While the Bernoulli equation would forecast that the highest wind speeds occur in the narrowest part of the wind gap, Sharp states that the highest speed (and most turbulent air movement) is actually found west of the gap’s exit point. Also on the leeward side of the gap, drastic vertical air movements and turbulence are caused by deflection off ridges and high points, widening of the Gorge below the gap, and formation of “mountain waves” below the gap and barriers. As a result of the descent and rapid mixing of air at and below the inversion, any clouds present west of the crest typically dissipate as the air rushes through the gap and on toward Portland and the ocean under clear skies.
It’s therefore apparent that some very unique and drastic changes in Gorge meteorology occur adjacent to Shellrock Mountain during the coldest periods of the year, perhaps capable of driving the supercharged overcooling of talus slopes required for the formation of periglacial ice. But how might this occur?
A simple thought experiment could present part of the mechanism. Let’s suppose that two hot air balloonists were brave enough to make matching flights from either side of the Wind/Shellrock gap during a typical Gorge east wind event. One launches into the overcast inversion from Cooks Landing about one mile east of the gap, as the other launches into the clear skies from Wyeth about one mile west of the gap. The one launching from Cooks would ascent fast through the cold and dense air near the surface, until he met the warmer air above. At this point, his ascent would slow or even stop because of the slight relative difference between the temperature inside his balloon’s envelope and the temperature of the warm air above the inversion boundary. The balloonist launching from Wyeth would have a much different ride as his flight progresses. His initial rate of ascent would be about the same as the balloonist at Cooks, given the ground temperatures at the two locations are equivalent and the two balloon envelopes were charged to the same temperature. His ascent would not slow or stop, however, at the elevation of the now absent inversion boundary. Instead, he would continue rising quickly, as long as the temperature within his balloon’s envelope was warmer than the surrounding air.
Just as a balloon’s flight is liberated skyward with the elimination of an air inversion, so might the upward flow of warm air within a western Gorge talus slope, since both are controlled by relative differences in temperature between the outside and inside. During the winter (as depicted by the figure in Chapter 2), heat stored in the upper slope from the prior summer rises within the interior air to the top of the slope where it discharges. As this occurs, a dynamic low is created at the bottom of the slope that draws cold winter air into talus at the base. The rate of upslope movement (and therefore the intensity of the chimney effect cooling mechanism) is maximized when the outside air is coldest, especially at the top of the slope. Such conditions are most likely to occur when there is no inversion layer, as occurs on the lee side of the Wind/Shellrock gap during the persistent, cold, continental air, east wind events of winter.
Note that while this explanation poses one possible explanation for the presence of apparent permafrost at the Wind/Shellrock gap, the theory is a little shaky, given that the strongest winter inversion layers are usually at about 1,500 feet, and therefore above the subject talus slope that spans 120-800 feet elevation. Nevertheless, it may be possible that lower altitude inversions exist at certain times that slow air movement through talus during the critical cooling periods. And again, the absence of such conditions west of the wind gap could accelerate upward flow, and therefore, the rate of cooling at the base of west Gorge talus slopes.
While this “inversion breakup explanation” may partially explain the strong cold talus mechanism at Shellrock, other factors could be involved too. First, given the fact that clear skies are more likely west of the Wind/Shellrock gap during the coldest time of the year, it is likely that radiative cooling (i.e., infrared heat emission from the land surface into outer space during long winter nights), is most intense here. Intensive radiative cooling occurs mainly on landscapes that lack infrared-blocking vegetation, fog or clouds. Such clear atmospheric conditions are typical in the western Gorge during cold winter, high pressure weather systems. Second, it could be possible that the wildly turbulent pressure patterns (and resultant winds) on the leeward (i.e., west) end of Shellrock are responsible for directly driving cold air into the base of the slope. At the same time, these currents could be locally reducing pressures at the top of the slope, thus directly accelerating the flush of warm air from vents at the top and increasing the suction of cold air into the lower slope.
Third, the possible existence of ice-cored talus on the Oregon side of the western Gorge might be partially due to unique Gorge geology and topography, combined with a physical process known as the “Balch effect”. The American explorer Edwin Swift Balch was perhaps the first scientist to note, inventory and explain the presence of localized, small periglacial ice features in Europe and America, including our own well-known Ice Cave some five miles WSW of Trout Lake, Washington. Balch termed such features “Glacières”, or “freezing caverns” in his book published in 1900. While Balch understood and described what is now termed the chimney effect, he recognized an even more basic mechanism that explains the formation of some underground ice features. Balch effect cooling is driven simply by the fact that cold air, being denser than warm air, will flow downslope to fill low and contained openings in the landscape. He found that such openings or pockets could include caves, mines, wells, porous talus fields, and rock fissures. Balch theorized that such pockets could become perpetually frozen (i.e., decoupled from the upper air environment) by the seasonal flushing of warm air with cold air, persistence of the sunken cold and dense air mass, topographical shading, and the insulating behavior of the surrounding rock and air pockets.
For Balch effect cooling at western Columbia River Gorge talus fields to result in conditions something akin to the Trout Lake Ice Cave, it would be assumed that the talus at the base of such slopes would need to be topographically shaded, relatively deep, and contained in a closed topographic depression to prevent escape of cold air from the slope. In the case of Shellrock Mountain, shading, volume and depth of talus at the mountain’s base is likely very high due to the mountain’s size and the talus proximity to the steep north cliffs. There is additionally at least one geological mechanism that could have resulted in a bowl-like containment of the talus around the northern base of the mountain, that being the past deposition of landslide and/or alluvial debris from both the Oregon and Washington sides of the Columbia. The possibility that such debris flowed across the Columbia River from the Washington side is not that remote, given the location of the Wind Mountain Landslide due north and oriented directly at the north side of Shellrock Mountain (see diagram below). If such inundation of the relatively older talus slopes did occur from the north and west, it could have formed containment for cold air sinking into the lower talus margins, thus creating a Balch effect-caused permafrost environment.
Finally, it is important to interject here that whatever cooling mechanism is dominant at Shellrock Mountain (chimney effect, Balch effect, etc.), a very cold source of air during the over-cooling period would be necessary to drive refrigeration at the base of the mountain. As ventured in Chapter 5, this source is likely east wind events, though it is possible that cooling is being intensified by localized drainage of cold air from the north slopes of 4,960 foot Mt. Defiance, and other high western Gorge peaks overlooking the 20 mile-long “pika belt”. Such downslope flows of intensely cold air would likely be occurring during the clear nights and morning that follow cloudy days. Cloudy conditions during the preceding day would not allow much warming of the land surface prior to the cold night.
Ice Mountain: The Course of Re-discovery — Chapter 6
A century ago, the frozen feature at Shellrock Mountain was probably just a local curiosity, though it did have real-world impacts on the construction and maintenance of the 1915 Columbia River Highway. After the road was abandoned, the feature was mostly forgotten in absence of the old highway’s framework. Today, however, it might assume several new and important contexts. First, the feature is likely an important engineering and interpretive consideration with respect to the re-born Historic Columbia River Highway Trail. Second, it has very important scientific study and interpretive values, especially if confirmed as anomalously low permafrost and periglacial ice for this elevation and latitude. Third, its presence may have bearing on the future of a little understood species that is subject to changes in climate and alterations to its habitat. While American pikas are far from being imperiled across their total North American range, most scientists would agree that they could be threatened along the fringes of this range. The Gorge’s unique low-elevation pikas would certainly be considered one such fringe population.
A Way Forward
The current day observation of the cold talus mechanism and possible permafrost at the base of Shellrock Mountain (and other talus slopes in the western Gorge’s 20 mile long “pika belt”) opens a wide variety of future geological, biological, meteorological, and climate-related study opportunities.
Foremost, is the opportunity for geological work to confirm and explain permafrost and periglacial ice at this nearly sea-level location. Research of this type is increasing in places like the Alps due to the fact that so much human infrastructure is in close proximity to glacial and periglacial slopes that may become unstable during a warming climate.
Researchers interested in understanding cold talus and permafrost in talus slopes use three primary study techniques, including: a) continuous temperature monitoring along slope profiles, b) boreholes designed to intercept subsurface ice for logging and long-term temperature monitoring, and c) geophysical investigations relying on the use of ground resistivity logging. While the last two methods can definitely prove the existence of permafrost and ice, temperature monitoring along slope profiles is at least capable of illustrating the strength of the cold talus mechanism and the likelihood of frozen conditions. This spring, I am hoping to begin monitoring slope profile temperatures in partnership with researcher Connie Millar of the USFS, and land managers including ODOT and USFS National Scenic Area office in Hood River. Beyond that, it is hoped that others (perhaps Oregon Department of Geology and Mineral Industries, private industries, and universities) might have the ability to conduct the larger work of drilling boreholes, performing aerial thermal photogrammetry, and conducting geophysical surveys to find direct evidence of permafrost and periglacial ice.
Regardless of whether permafrost and ice is proven, the unique cold talus slopes of the western Gorge represent wonderful laboratories for the examination and interpretation of the anomalous, out-of-place biological features (fungi, mosses, vascular plants, amphibians, mammals, birds, etc.) that surround cold talus vents. Perhaps most interesting would be a study intended to see whether Shellrock Mountain pika population are shifting closer to the base of cold talus slopes in response to climate-induced warming of their middle altitude ranges. It has usually been assumed that pikas are only being driven to higher elevations in response to warming, but the inverse may also be true. Unfortunately, those being forced downslope to the base of the Gorge’s cold talus slopes could one day be genetically isolated from the larger upper populations. Taken to the extreme, if the cold talus cooling mechanism becomes less intense over time, the low elevation cold talus refuge could disappear altogether, which might spell the end of our unique low-elevation population. Also interesting would be the study of whether pikas seasonally migrate up-and-down individual talus slopes to take advantage of optimal thermal conditions. It may be possible that they shift downward toward the cool vent areas during the summer for heat shelter and food collection, and then shift upward toward warmer vent zones to survive the winter’s cold and wetness.
Next, there is the great opportunity to tie understanding of all these issues using a biogeographic approach, which would hopefully uncover the complex mix of atmospheric and geologic influences that account for intense cold talus, potential permafrost, and other habitat features at Shellrock Mountain and other locations in the western Gorge’s low elevation “pika belt”. One interesting study would be a focus on the importance of talus rock type (including composition, size and shape) on pika habitat suitability in the Gorge. Worldwide, talus slopes can be derived from most any bedrock type that occurs in the overlooking headwalls, but in the Gorge these are mainly limited to the two igneous rock types basalt and quartz diorite. The twin intrusive volcanic necks of Shellrock Mountain and Wind Mountain are both composed of quartz diorite, which is somewhat lighter in weight and color than basalt. Quartz diorite cliffs also tend to shed a more flattened and plate-shaped talus, which could have important implications on the size and shape of pika pocket openings, thermal insulation, sun shading, pocket roofing (water shedding character), and suitability for the dry storage of the pika’s “hay piles”.
Finally, as described in the fifth chapter, the topographic Wind/Shellrock wind gap is one of the most dominant meteorological features of the Gorge, and could account for the apparent over-cooling of talus slopes occurring in the western Gorge during winter. Gaining complete understanding of the mechanism will be a significant job that involves installation of several meteorological monitoring sites around the wind gap, followed by fine-scale modelling of the turbulent wind directions, temperatures and pressure patterns. As meteorologist Justin Sharp has ventured to say, conventional weather modelling techniques would not be able to unmask the complex air circulations and pressure patterns on the sides of Shellrock Mountain. In his estimation, understanding would best rely on “computational fluid dynamics” (CFD) modelling to trace the likely air flows and talus heat transfers. CFD modelling, using the fastest of our supercomputers, is the tool that aeronautic engineers use to model complex airflows around aircraft and inside turbine engines. Such methods are also used at the landscape scale by the wind power industry and others to understand flows surrounding wind turbines, buildings, bridges, etc., and associated topographic features.
I thank Dr. Connie Millar of the US Forest Service and Dr. Justin Sharp of Sharply Focused LLC for their review, and for noting likely pitfalls contained in this very theoretical work. I also thank Susan Hess (www.envirogorge.com) for editing suggestions.
Comments on this article can be posted below, or via email at email@example.com.
About Steve Stampfli
Steve Stampfli was born and raised in Denver and the mountains of Colorado. He obtained his bachelor’s degree in biology from Colorado College in 1975, and masters’ degree in environmental management from Duke University in 1979. From there, he pursued interests in landscape restoration working as director of the Exploration and Mining Program for the state of South Dakota, and then as environmental coordinator for Wharf Resources Inc. Annie Creek Gold Mine in the Black Hills. He moved to the Gorge in 1988, where he worked as manager of the Underwood Conservation District for fourteen years, and then five years as coordinator of the Hood River Watershed Group. Since retirement he has continued working on various projects that relate to one of his main life interests, that being the reclamation and restoration of disturbed landscapes.